AT&T MERLIN LEGEND System Reference Manual page 70

Features
Feature Interactions
Automatic Maintenance
Busy
Direct-Line Console
Inspect
Personal Lines
Pools
Queued Call Console
System Programming
The red LED goes on next to the Alarm buttons on system operator consoles,
and the designated Maintenance Alarm alert device sounds or flashes when
more than 50 percent of the trunks in the trunk pool are in a maintenance-busy
state.
The DLC system operator uses an Alarm button to monitor system operation. A
system operator with a digital DLC can use Inspect to display the number of
alarms: a system operator with an analog DLC cannot use Inspect.
On a small system (fewer than 29 lines), an Alarm button is factory-assigned to
analog DLCs with 34 buttons or more. On a large system (more than 29 lines),
the Alarm button is replaced with line 30. An Alarm button is factory-assigned to
an MLX-28D used as a DLC, regardless of the number of lines/trunks connected
to the system. The Alarm button is not a fixed feature and can be assigned to
any available button on an analog or digital DLC.
Inspect can be used on a digital DLC or a QCC to display the number of alarms;
Inspect cannot be used on an analog DLC.
A line/trunk jack used for a Maintenance Alarm cannot be assigned as a
personal line.
A trunk jack used for a Maintenance Alarm cannot be assigned to a trunk pool
(Hybrid/PBX only).
An Alarm button is assigned as a fixed feature on a QCC.
Designate line/trunk jack that connects an external alerting device used for
Alarm.
AuxEquip -> MaintAlarms
Alarm 2-21